Regarding red hat subscription

[ganirudh]

I recently bought HP intel based x86 servers for my lab. I have to install RHEL 5.4 on these servers.

I was going through RedHat page and found that I need to buy some sort of subscriprions from red hat to install RHEL.

I want to know if I can install RHEL 5.4 on these servers without buying subscriptions from red hat or it is absolutely necessary to buy subscription from red hat.

[Irithori]

If you want/need RedHat, you need a subscription.

However, there is a free (as in beer) alternative: CentOS.
It is 99,99% the same (compiled from the same source and versions)

[Rubberman]

You can apply for a limited-time (30 days I think) license for real RHEL 5.4, but you will have to purchase support licenses in order to continue to get updates. As Irithori mentioned, CentOS is the community version of RHEL (I am using it right now), and there are other versions as well, such as Scientific Linux, that are very stable and directly compiled from RHEL sources, just without the RedHat logos, etc. A lot of major commercial servers, such as systems running major stock/options exchanges, are run with CentOS, and most major university and government scientific systems are run with Scientific Linux, such as FermiLab, Argonne National Lab, CERN, etc.